Preparation method of silicon carbide wafer
By using a multi-stage grinding process and reverse rotation combined with grinding aids, the problems of microcracks and edge chipping in the thinning process of silicon carbide wafers were solved, and high-quality and high-performance silicon carbide wafer production was achieved.
Patent Information
- Application Number
- CN202610065050.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-19
- Publication Date
- 2026-02-17
AI Technical Summary
Existing silicon carbide wafers are prone to microcracks and edge chipping during the thinning process, which affects their surface quality and performance.
A multi-stage grinding process is adopted, which controls grinding force and temperature by setting the workpiece and the support table to rotate in opposite directions, combined with the use of grinding additives, and gradually reducing the feed rate to improve grinding uniformity and stability.
It significantly reduces the chipping rate of silicon carbide wafers, improves surface quality and performance, and enhances processing yield and process reliability.
Smart Images
Figure CN121535602A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a method for preparing silicon carbide wafers. Background Technology
[0002] Silicon carbide (SiC), also known as silicon carbide, carborundum, or refractory sand, is a refractory material produced by high-temperature smelting of quartz sand, petroleum coke (or coal coke), and sawdust in an electric resistance furnace. Silicon carbide also exists in some rare natural minerals, such as moissanite. As a typical third-generation semiconductor material, silicon carbide possesses characteristics such as a wide bandgap, high electron mobility, high critical breakdown field strength, and high thermal conductivity, making it widely applicable in power electronics, high-frequency communications, high-temperature sensing, and high-power and high-temperature electronic devices. Furthermore, among contemporary non-oxide high-tech refractory raw materials such as C, N, and B, inexpensive silicon carbide is widely used as a core material in the fields of refractory materials, abrasives, and advanced ceramics. Currently, industrially produced silicon carbide mainly includes green silicon carbide with a purity greater than 99% and black silicon carbide with a purity of 95%–98%. However, microcracks are prone to occur in the edge areas when silicon carbide is thinned. As the application fields of silicon carbide continue to expand and deepen, the industry has put forward increasingly stringent requirements for the quality and performance of silicon carbide wafers.
[0003] Therefore, in order to improve the quality and performance of silicon carbide wafers, it is urgent to optimize a manufacturing process that can produce silicon carbide wafers with high surface quality and performance. Summary of the Invention
[0004] One objective of this application is to provide a method for preparing silicon carbide wafers, which helps to reduce the chipping rate of silicon carbide wafers and further improve the surface quality and performance of silicon carbide wafers.
[0005] To achieve the above objectives, the technical solution adopted in this application is as follows: a method for preparing a silicon carbide wafer, comprising the following steps: S100, placing the wafer to be processed on a support stage, and using a grinding tool to perform rough grinding on the wafer to be processed, wherein the grinding tool grinds the wafer to be processed to a depth of 20μm~50μm to obtain a first wafer; S200, rotating the support stage and the grinding tool in opposite directions, and using the grinding tool to perform fine grinding on the first wafer to obtain a silicon carbide wafer, wherein the grinding tool grinds the first wafer to a depth of 10μm~30μm, the rotational speed of the support stage is w1, and the rotational speed of the grinding tool is w2, wherein 0.05w2≤w1≤0.25w2.
[0006] In some embodiments, in step S200, the rotational speed of the support stage is 200 rpm to 500 rpm, the rotational speed of the grinding element is 2000 rpm to 4000 rpm, and the grinding element grinds the first wafer along the thickness direction of the first wafer at a feed rate of 0.2 μm / s to 1 μm / s.
[0007] In some embodiments, step S200 includes the following sub-steps: S210, rotating the support stage in the opposite direction to the grinding member, the grinding member grinding the first wafer along the thickness direction of the first wafer at a first feed speed to obtain a first intermediate wafer, the first feed speed being 0.5 μm / s to 1 μm / s, and the grinding member grinding the first wafer to a depth of 8 μm to 15 μm; S220, maintaining the opposite rotation direction of the support stage to the grinding member, the grinding member grinding the first intermediate wafer along the thickness direction of the first intermediate wafer at a second feed speed. The second feed speed is 0.3μm / s to 0.8μm / s, which is less than the first feed speed. The grinding element grinds the first intermediate wafer to a depth of 4μm to 8μm to obtain the second intermediate wafer. S230: Keeping the rotation direction of the support stage opposite to that of the grinding element, the grinding element grinds the second intermediate wafer along the thickness direction of the second intermediate wafer at a third feed speed of 0.1μm / s to 0.5μm / s, which is less than the second feed speed. The grinding element grinds the second intermediate wafer to a depth of 1μm to 4μm.
[0008] In some embodiments, step S200 further includes the step of: during the grinding process, sputtering a grinding aid onto the first wafer, wherein the dispersion of the grinding aid is one or more of a metal oxide, a metal sulfide, or a metal chloride, and the dispersion medium is water.
[0009] In some embodiments, the dispersion of the grinding aid is one or more of nano zinc oxide and nano zinc sulfide, and the volume fraction of the dispersion in the grinding aid is 1% to 4%.
[0010] In some embodiments, the side of the first wafer that is being ground is called the grinding surface, and the grinding surface forms an angle α with the sputtering direction of the grinding aid, the angle α being 45°~90°.
[0011] In some embodiments, the temperature of the grinding aid is 15°C to 40°C, so that the temperature of the first wafer is kept below 100°C during the grinding process in step S200.
[0012] In some embodiments, step S100 further includes the following steps: S110, providing a support stage for holding a wafer to be processed, and a grinding element for grinding the surface of the wafer to be processed, rotating the grinding element and the wafer to be processed, so that the grinding element grinds the wafer to be processed, the rotation speed of the grinding element is 2000 rpm to 4000 rpm, and the rotation speed of the support stage is 200 rpm to 500 rpm; S120, grinding the wafer to be processed by the grinding element along the thickness direction of the wafer to be processed at a feed speed of 0.4 μm / s to 1 μm / s, in the single grinding process, the grinding element grinds the wafer to be processed to a depth of 3 μm to 12 μm, and repeating the single grinding process multiple times until the grinding element grinds the wafer to be processed to a depth of 20 μm to 50 μm.
[0013] In some embodiments, step S200 is followed by step S300, which is: cleaning and drying the support stage and the silicon carbide wafer using a water-air two-fluid system.
[0014] In some embodiments, the wafer to be processed is a 4H-SiC substrate material.
[0015] Compared with the prior art, the beneficial effects of this application are as follows: (1) This application divides the grinding process of silicon carbide wafers into multiple stages, and sets grinding parts and wafers with different rotation states in different stages, which is beneficial to reducing the chipping rate of silicon carbide wafers. In other words, this application first grinds the wafer with a unidirectional rotating grinding part, which is beneficial to achieve uniform preliminary thinning of the wafer and obtain a wafer with a flat surface. On this basis, the grinding part and the wafer are rotated in opposite directions to increase the uniformity of grinding on the wafer surface, thereby increasing the surface quality, high consistency and local flatness of the wafer. Furthermore, the reverse rotation is beneficial to provide uniform grinding force when grinding the wafer, thereby reducing the occurrence of microcracks or chipping caused by stress concentration, reducing the chipping rate of silicon carbide wafers, and further improving the surface quality and performance of silicon carbide wafers. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of sputtering a grinding aid onto the surface of a first wafer.
[0017] Figure 2 A schematic diagram of the area where grinding aids are sprayed onto the surface of the first wafer.
[0018] Figure 3 This is an optical microscope image of the silicon carbide wafer in Example 1.
[0019] Figure 4This is an optical microscope image of the silicon carbide wafer in Comparative Example 1.
[0020] In the figure: 10, first wafer; 101, grinding surface; 20, first virtual circle; 30, second virtual circle. Detailed Implementation
[0021] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.
[0022] As used herein, the terms “prepared from” and “comprising” are synonymous. The terms “comprising,” “including,” “having,” “containing,” or any other variation thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements and may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.
[0023] When a quantity, concentration, or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range is disclosed as “1 to 5”, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range includes its endpoints and all integers and fractions within that range.
[0024] Approximate terms used in the specification and claims to modify quantities indicate that the invention is not limited to that specific quantity, but also includes acceptable modifications close to that quantity that do not alter the relevant essential function. Correspondingly, the use of "about," "approximately," etc., to modify a numerical value means that the invention is not limited to that precise value. In some instances, approximate terms may correspond to the precision of the instrument used to measure the value. In this application's specification and claims, scope definitions can be combined and / or interchanged, unless otherwise stated, these scopes include all subscopes contained therein.
[0025] The applicant discovered that 4H-SiC wafers, as a core high-end material in the semiconductor industry, are widely used in various new energy industries, power device markets, and photovoltaic energy storage. However, 4H-SiC wafers are somewhat brittle and difficult to process, thus limiting their widespread application.
[0026] Therefore, as Figure 1 and Figure 2 It is understood that this application provides a method for preparing a silicon carbide wafer, including the following steps: S100, placing the wafer to be processed on a support stage, and using a grinding tool to perform rough grinding on the wafer to be processed, with the grinding tool grinding the wafer to be processed to a depth of 20μm~50μm, to obtain a first wafer 10; S200, making the rotation direction of the support stage and the grinding tool opposite, and using the grinding tool to perform fine grinding on the first wafer 10 to obtain a silicon carbide wafer, with the grinding tool grinding the first wafer 10 to a depth of 10μm~30μm, the rotation speed of the support stage being w1, and the rotation speed of the grinding tool being w2, wherein 0.05w2≤w1≤0.25w2.
[0027] It should be understood that this application, by dividing the grinding process of silicon carbide wafers into multiple stages and setting grinding tools and wafers with different rotation states in different stages, is beneficial to reducing the chipping rate of silicon carbide wafers. In other words, this application first grinds the wafer to be processed using a unidirectional rotating grinding tool, which is beneficial to achieve uniform initial thinning of the wafer and obtain a first wafer 10 with a flat surface. On this basis, the grinding tool and the support stage are rotated in opposite directions to increase the uniformity of grinding on the surface of the first wafer 10, reduce the impact of the grinding tool on the wafer edge, and thus increase the surface quality, high uniformity, and local flatness of the obtained silicon carbide wafer. Furthermore, the reverse rotation is beneficial to provide uniform grinding force during wafer grinding, thereby reducing the occurrence of microcracks or chipping caused by stress concentration, reducing the chipping rate of silicon carbide wafers, and further improving the surface quality and performance of silicon carbide wafers.
[0028] It is worth noting that because the grinding workpiece and the support table rotate in opposite directions in some steps, meaning that the linear velocities of the grinding workpiece and the wafer are opposite during frictional contact, the relative velocity is the sum of their linear velocities. This improves the stability and efficiency of the grinding process. Furthermore, the reverse rotation reduces the impact of the grinding workpiece on the wafer edge, which helps reduce the chipping rate of silicon carbide wafers. Conversely, when the grinding workpiece and the support table rotate in the same direction, the relative velocity is the difference between the linear velocities of the grinding workpiece and the wafer. This causes drastic changes in their positions during grinding, increasing the risk of unstable grinding force, thus reducing grinding quality and increasing the chipping rate of silicon carbide wafers.
[0029] It is understandable that in step S200, the rotational speed of the support stage is w1, and the rotational speed of the grinding element is w2, where 0.05w2≤w1≤0.25w2. Specifically, the value of w1 can be 0.05w2, 0.10w2, 0.15w2, 0.20w2, or 0.25w2. It should be understood that because the rotational speed of the grinding element is much greater than that of the support stage, the grinding element can stably and efficiently grind the first wafer 10, thereby reducing the chipping rate of the silicon carbide wafer. On the one hand, when the grinding element is a grinding wheel, the scratching trajectory of a single abrasive grain on the surface of the high-speed rotating grinding wheel is shorter and shallower on the surface of the first wafer 10, which is beneficial to reducing the surface roughness of the silicon carbide wafer. At the same time, it can also reduce the lateral component of the grinding force generated on the surface of the first wafer 10, thereby suppressing the initiation and propagation of microcracks in the silicon carbide wafer and further enhancing the surface quality of the silicon carbide wafer.
[0030] In some embodiments, the grinding element is a grinding wheel. The grinding wheel has excellent material removal performance, enabling uniform grinding of silicon carbide wafers with high hardness through the abrasive grains on the wheel, and rapidly thinning the silicon carbide wafer to the target thickness, which is beneficial for large-scale production. On the one hand, because the support platform carrying the silicon carbide wafer rotates in opposite directions to the grinding wheel during the grinding process, the locking force between the carrier plate and the spindle component in the grinding wheel can be reduced, which helps to increase the uniformity of the frictional force generated when the grinding wheel grinds the silicon carbide wafer.
[0031] In some embodiments, the rotational speed of the support stage in step S200 is 200 rpm to 500 rpm, specifically, the rotational speed of the support stage is 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, or 500 rpm; the rotational speed of the grinding element is 2000 rpm to 4000 rpm, specifically, the rotational speed of the grinding element is 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, or 4000 rpm; the grinding element moves along the thickness of the first wafer 10. The first wafer 10 is ground at a feed rate of 0.2 μm / s to 1 μm / s. Specifically, the feed rate of the grinding tool is 0.2 μm / s, 0.3 μm / s, 0.4 μm / s, 0.5 μm / s, 0.6 μm / s, 0.7 μm / s, 0.8 μm / s, 0.9 μm / s, and 1 μm / s. The grinding depth of the first wafer 10 is 10 μm to 30 μm. Specifically, the grinding depth of the first wafer 10 is 10 μm, 15 μm, 20 μm, 25 μm, and 30 μm. By selecting appropriate rotation speeds for the first wafer 10 and the grinding tool, it is beneficial to obtain silicon carbide wafers with good surface quality and low edge chipping rate, which is conducive to stable subsequent processing.
[0032] In some embodiments, step S200 includes the following sub-steps: S210, the rotation directions of the support stage and the grinding member are opposite, and the grinding member grinds the first wafer 10 along the thickness direction of the first wafer 10 at a first feed speed to obtain a first intermediate wafer, the first feed speed being 0.5μm / s~1μm / s, and the grinding member grinding the first wafer 10 to a depth of 8μm~15μm; S220, keeping the rotation directions of the support stage and the grinding member opposite, the grinding member grinds the first intermediate wafer along the thickness direction of the first intermediate wafer at a second feed speed, the first... The second feed rate is 0.3μm / s to 0.8μm / s, which is less than the first feed rate. The grinding workpiece grinds the first intermediate wafer to a depth of 4μm to 8μm to obtain the second intermediate wafer. S230: Keeping the rotation direction of the support stage and the grinding workpiece opposite, the grinding workpiece grinds the second intermediate wafer along the thickness direction of the second intermediate wafer at a third feed rate of 0.1μm / s to 0.5μm / s, which is less than the second feed rate. The grinding workpiece grinds the second intermediate wafer to a depth of 1μm to 4μm.
[0033] Understandably, dividing the grinding process into three progressive stages helps to release stress on the silicon carbide wafer step by step during grinding, with the feed rate gradually decreasing. This allows for uniform control of grinding force changes during grinding, reducing the risk of edge chipping in the silicon carbide wafer. Furthermore, because the multi-stage grinding process allows for easy transitions, it has a higher tolerance for fluctuations in equipment and wafer initial conditions. This means that even if minor changes occur in the grinding conditions in step S210, they can be corrected and converged in subsequent steps, ultimately resulting in a stable output of silicon carbide wafers with good surface quality, further improving production yield and process reliability. In step S220, the feed rate is reduced compared to step S210, which helps to reduce the risk of dynamic imbalance during grinding and further enhances the stability of the processing environment. Furthermore, in step S230, the feed rate is further reduced to grind the second intermediate wafer under gentler conditions, thereby suppressing the generation and propagation of microcracks and avoiding excessive heat generated by friction due to excessively high feed rates.
[0034] In some embodiments, in step S210, the first feed rate can be 0.5 μm / s, 0.6 μm / s, 0.7 μm / s, 0.8 μm / s, 0.9 μm / s, or 1 μm / s. More preferably, the feed rate of the grinding element along the thickness direction of the first wafer 10 is 0.6 μm / s. The grinding depth of the first wafer 10 is 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm. More preferably, the grinding depth of the first wafer 10 is 10 μm. By selecting a suitable stage for supporting the first wafer 10 and the rotational speed of the grinding element, it is beneficial to obtain a first intermediate wafer with good surface quality and low chipping rate, thereby facilitating stable subsequent processing.
[0035] In some embodiments, in step S220, the second feed rate can be 0.3 μm / s, 0.4 μm / s, 0.5 μm / s, 0.6 μm / s, 0.7 μm / s, or 0.8 μm / s; the rotational speed of the first intermediate wafer is 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, or 500 rpm; and the grinding depth of the first intermediate wafer by the grinding element is 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm. By selecting appropriate support stages for the first intermediate wafer and rotational speeds of the grinding element, it is beneficial to obtain second intermediate wafers with good surface quality and low chipping rate, thereby facilitating stable subsequent processing.
[0036] In some embodiments, in step S230, the third feed rate can be 0.1 μm / s, 0.2 μm / s, 0.3 μm / s, 0.4 μm / s, or 0.5 μm / s; the rotational speed of the second intermediate wafer is 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, or 500 rpm; and the grinding depth of the second intermediate wafer by the grinding element is 1 μm, 2 μm, 3 μm, or 4 μm. By selecting appropriate bearing stages for the second intermediate wafer and rotational speeds of the grinding element, it is beneficial to obtain silicon carbide wafers with good surface quality and low edge chipping rate, thereby facilitating subsequent stable processing.
[0037] In some embodiments, step S200 further includes the step of: during the grinding process, sputtering a grinding aid onto the first wafer 10, wherein the dispersion of the grinding aid is one or more of a metal oxide, a metal sulfide, or a metal chloride, and the dispersion medium is water. It is worth noting that, to prevent a decrease in precision due to excessive friction in the grinding element, sputtering the grinding aid during the grinding process allows the grinding element to grind the wafer more uniformly. On the other hand, when the grinding element is subjected to high-load processing for a long time, the processing precision of the grinding element will decrease. Therefore, compared to not sputtering the grinding aid, sputtering the grinding aid can reduce the interface temperature between the grinding element and the wafer surface by 30% to 40% during grinding, thereby facilitating the cutting of the wafer by the grinding element.
[0038] It is worth mentioning that since a large amount of heat is generated on the wafer surface during grinding, grinding aids with metal oxides, metal sulfides, or metal chlorides as dispersions can reduce the temperature of the wafer surface in the high-temperature environment generated by grinding, thereby helping to reduce the processing difficulty of the wafer and further enhance the processing accuracy of the wafer.
[0039] In some embodiments, the dispersed phase of the grinding aid is one or more of nano-zinc oxide and nano-zinc sulfide, and the volume fraction of the dispersed phase in the grinding aid is 1% to 4%, specifically, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, and 4%. By selecting a suitable grinding aid for sputtering the first wafer 10, it is not only beneficial to alleviate excessive friction between the grinding workpiece and the first wafer 10, but also to better disperse and suspend the chips and abrasive particles generated during grinding in the grinding aid, preventing them from re-adhering to the surface of the grinding workpiece or wafer. Furthermore, nano-zinc oxide, as a good thermal conductor, can quickly dissipate the heat generated during grinding, preventing localized thermal stress damage. Nano-zinc sulfide has a layered structure and can act as a solid lubricant, preventing the reduction in precision caused by excessive friction in the grinding workpiece.
[0040] In some embodiments, such as Figure 1 As shown, the grinding surface 101 is the surface of the first wafer 10 being ground. An angle α is formed between the grinding surface 101 and the sputtering direction of the grinding aid, with the angle α being 45°~90°. By selecting a suitable sputtering direction of the grinding aid, it is beneficial to reduce the temperature of the grinding surface 101 and enhance the grinding uniformity.
[0041] In some embodiments, the dispersion and the dispersion medium are mixed in a storage tank to obtain a grinding aid, which is then sprayed onto the grinding surface 101 through a nozzle. At this time, the angle α formed between the grinding surface 101 and the spray direction of the grinding aid is the angle formed between the nozzle direction and the grinding surface 101.
[0042] In some embodiments, such as Figure 1 and Figure 2 As shown, the splashing point of the grinding aid forms a rinsing area on the grinding surface 101. The outer edge of the rinsing area forms a first virtual circle 20, and the outer edge of the grinding surface 101 forms a second virtual circle 30. The first virtual circle 20 and the second virtual circle 30 are concentric. The radius of the first virtual circle 20 is n1, and the radius of the second virtual circle 30 is n2, where 0.2n2 ≤ n1 ≤ 0.5n2. By selecting a suitable splashing point for the grinding aid, it is beneficial to reduce the temperature of the grinding surface 101, enhance grinding uniformity, and thus splash out impurity particles generated on the grinding surface 101 during grinding. It is worth mentioning that the splashing point of the grinding aid can be the center of the grinding surface to increase the uniformity of the splashed grinding aid.
[0043] In some embodiments, the temperature of the grinding aid is 15°C to 40°C, so that the temperature of the first wafer 10 is kept below 100°C during the grinding process in step S200. Specifically, the temperature of the grinding aid is 15°C, 20°C, 25°C, 30°C, 35°C, or 40°C. It should be understood that the grinding aid can cool the workpiece during grinding to reduce the grinding heat generated during the grinding process. However, it is worth mentioning that when the flow rate of the grinding aid is too high, a greater impact force is generated, which impacts the grinding wheel teeth in the grinding wheel, causing diamond particles on the grinding wheel to fall off, resulting in scratches on the wafer or impacts on the wafer edge, causing chipping. When the flow rate of the grinding aid is too low, it is easy to fail to flush the processing point, thereby reducing the cooling effect on the grinding surface 101. Therefore, by selecting a grinding aid with an appropriate flow rate, it is beneficial to reduce the temperature of the grinding surface 101, enhance the grinding uniformity, and thus flush out the impurity particles generated on the grinding surface 101 during grinding.
[0044] In some embodiments, step S100 further includes the following steps: S110, providing a support stage for holding the wafer to be processed, and a grinding element for grinding the surface of the wafer to be processed, rotating the grinding element and the wafer to be processed, so that the grinding element grinds the wafer to be processed, the rotation speed of the grinding element is 2000 rpm to 4000 rpm, and the rotation speed of the support stage is 200 rpm to 500 rpm; S120, grinding the wafer to be processed by the grinding element along the thickness direction of the wafer to be processed at a feed speed of 0.4 μm / s to 1 μm / s, in the single grinding process, the grinding depth of the grinding element on the wafer to be processed is 3 μm to 12 μm, and repeating the single grinding process multiple times until the grinding depth of the grinding element on the wafer to be processed is 20 μm to 50 μm. Since step S100 provides a wafer with a certain surface flatness and uniform grinding force for step S200, step S100 can quickly and stably remove the damaged layer, warping, and large undulations on the wafer surface caused by previous processes, such as wire cutting, thereby improving overall processing efficiency. In other words, the support stage in step S100 can be in the same or opposite direction of rotation as the grinding workpiece, which is beneficial for quickly thinning the wafer to be processed.
[0045] Furthermore, by performing single grinding multiple times until the wafer to be processed is gradually ground into the first wafer 10, the total removal amount is decomposed into multiple small steps. The cutting force generated by each grinding is extremely small, thereby avoiding brittle fracture, deep cracks and thermal damage caused by excessive grinding depth during single grinding.
[0046] In some embodiments, the grinding rotation speed in step S110 is 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, or 4000 rpm; and the feed rate of the grinding part in step S120 is 0.4 μm / s, 0.5 μm / s, 0.6 μm / s, 0.7 μm / s, 0.8 μm / s, 0.9 μm / s, or 1 μm / s. Selecting appropriate grinding parameters is beneficial for reducing the chipping rate of the wafer.
[0047] In some embodiments, step S200 is followed by step S300, which involves cleaning and drying the stage and the silicon carbide wafer using a water-air dual-fluid system. It should be understood that the stage is a vacuum chuck, and the water-air dual-fluid system simultaneously cleans both the silicon carbide wafer and the micron-sized adsorption pore array on the vacuum chuck, ensuring that the vacuum chuck provides uniform vacuum adsorption force to the wafer to be processed.
[0048] In some embodiments, the wafer to be processed is a 4H-SiC substrate material. The silicon carbide wafers prepared by the method provided in this application have excellent surface quality and performance, further enhancing their market competitiveness.
[0049] Example 1 A method for preparing a silicon carbide wafer, comprising the following steps: (1) Take a 6-inch 4H-SiC wafer and fix it on a vacuum chuck. Use a DISCO DFG-8640 grinding wheel with an outer diameter of 209 mm and a rotation speed of 3500 rpm to grind the wafer along the thickness direction at a feed speed of 0.6 μm / s. The grinding depth in a single pass is 4 μm. Repeat the grinding process multiple times until the wafer is thinned to 12 μm to obtain the first wafer.
[0050] (2) The grinding wheel speed is kept at 3500 rpm. The first wafer is rotated in the opposite direction to the grinding wheel rotation direction. The speed of the first wafer is 301 rpm. Grinding aid is sprayed at the center position of the first wafer. The grinding surface of the first wafer and the spraying direction of the grinding aid form an angle of 60°. The grinding workpiece first grinds 7 μm along the thickness direction of the first wafer at a feed rate of 0.6 μm / s, then grinds 5 μm at a feed rate of 0.4 μm / s, and then grinds 3 μm at a feed rate of 0.2 μm / s to obtain a silicon carbide wafer. The dispersion of the grinding aid is nano zinc oxide, the dispersion medium is deionized water, and the volume fraction of the dispersion is 2.5%.
[0051] (3) Use water and air two-fluids to clean and dry the vacuum chuck and silicon carbide wafer.
[0052] Example 2 The difference between Example 2 and Example 1 is that in step (2), the grinding element grinds 15μm along the thickness direction of the first wafer at a feed rate of 0.4μm / s to obtain a silicon carbide wafer.
[0053] Example 3 The difference between Example 3 and Example 2 is that the rotational speed of the grinding part is 3200 rpm.
[0054] Example 4 The difference between Example 4 and Example 2 is that the rotational speed of the grinding part is 3000 rpm.
[0055] Example 5 The difference between Example 5 and Example 2 is that the rotational speed of the grinding part is 3800 rpm.
[0056] Example 6 The difference between Example 6 and Example 2 is that the rotational speed of the first wafer is 351 rpm.
[0057] Example 7 The difference between Example 7 and Example 2 is that the rotational speed of the first wafer is 351 rpm and the rotational speed of the grinding part is 3200 rpm.
[0058] Example 8 The difference between Example 8 and Example 2 is that the rotational speed of the first wafer is 351 rpm and the rotational speed of the grinding workpiece is 3000 rpm.
[0059] Example 9 The difference between Example 9 and Example 2 is that the rotational speed of the first wafer is 401 rpm.
[0060] Example 10 The difference between Example 10 and Example 2 is that the rotational speed of the first wafer is 401 rpm and the rotational speed of the grinding workpiece is 3200 rpm.
[0061] Example 11 The difference between Example 11 and Example 1 is that the dispersion of the grinding aid is nano zinc sulfide.
[0062] Example 12 The difference between Example 12 and Example 1 is that the dispersion of the grinding aid is nano zinc oxide and nano zinc sulfide, with the volume fraction of nano zinc oxide being 2% and the volume fraction of nano zinc sulfide being 0.5%.
[0063] Example 13 The difference between Example 13 and Example 1 is that the dispersion of the grinding aid is nano zinc oxide and nano zinc sulfide, with a volume fraction of 1.25% for both nano zinc oxide and nano zinc sulfide.
[0064] Example 14 The difference between Example 14 and Example 1 is that the grinding aid in step (2) is only water.
[0065] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that in step (2), the grinding workpiece and the support table rotate in the same direction, and the rotation speed of the grinding workpiece is 3500 rpm and the rotation speed of the support table is 301 rpm.
[0066] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the support platform does not rotate in step (2).
[0067] Performance testing The ratio of edge chipping phenomena in 2000 silicon carbide wafers prepared by the preparation methods provided in each of Examples 1 to 14, and in 200 silicon carbide wafers prepared by the preparation methods provided in Comparative Examples 1 and 2, was statistically analyzed to obtain the edge chipping rate statistics table shown in Table 1.
[0068] Table 1: Surface Testing of Silicon Carbide Wafers
[0069]
[0070] Depend on Figure 3 as well as Figure 4 The comparison shows that, Figure 3 This demonstrates the complete boundary of a silicon carbide wafer, while Figure 4 The image shows a silicon carbide wafer boundary exhibiting edge chipping, and when edge chipping occurs in the silicon carbide wafer... Figure 4 When the phenomenon shown in Table 1 occurs, it is determined that edge chipping has occurred in the silicon carbide wafer. Therefore, based on the probability of edge chipping as shown in Table 1, by introducing a step-by-step grinding process in step (2), the edge chipping rate can be reduced to below 0.2% compared to the 3%~5% chipping rate in traditional grinding processes, thereby reducing the risk of workpiece scrap or rework due to edge chipping. On this basis, further correlation control is applied to process parameters such as feed rate, rotational speed, and grinding aids to reduce the microcrack phenomenon caused by excessive grinding force or thermal damage to the wafer. Simultaneously, this application employs a water-air two-fluid cleaning technology to avoid blockage of the vacuum suction holes in the vacuum chuck, or insufficient or uneven vacuum pressure, thereby reducing the slight sliding or vibration phenomena generated during the grinding process and further reducing the risk of corner defects caused by abnormal stress on the wafer edge.
[0071] The preparation method provided in this application not only improves the processing yield of silicon carbide wafers with high hardness, but also reduces the probability of edge chipping larger than 50 μm by 20%, and reduces the chipping size from over 50 μm to below 20 μm. This further reduces the risk of edge chipping causing scratches during grinding and polishing, and improves the first-pass yield of grinding and polishing. It is worth mentioning that the first-pass yield of traditional silicon carbide wafer grinding and polishing is only 70%, while the first-pass yield of silicon carbide wafers prepared by the method provided in this application is greater than 96%.
[0072] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.
Claims
1. A method of producing a silicon carbide wafer, characterized by, The method comprises the steps of: S100, placing a wafer to be processed on a carrier table, and coarsely grinding the wafer to be processed by using a grinding tool, wherein the grinding tool grinds the wafer to be processed by a depth of 20-50 μm to obtain a first wafer; S200, rotating the carrier table in a direction opposite to that of the grinding tool, and finely grinding the first wafer by using the grinding tool to obtain a silicon carbide wafer, wherein the grinding tool grinds the first wafer by a depth of 10-30 μm, the rotating speed of the carrier table is w1, and the rotating speed of the grinding tool is w2, and 0.05w2≤w1≤0.25w2.
2. The production method according to claim 1, characterized by, In the step S200, the rotating speed of the carrier table is 200-500 rpm, the rotating speed of the grinding tool is 2000-4000 rpm, and the grinding tool grinds the first wafer along the thickness direction of the first wafer at a feeding speed of 0.2-1 μm / s.
3. The production method according to claim 2, characterized by, The step S200 comprises the following sub-steps: S210, rotating the carrier table in a direction opposite to that of the grinding tool, and grinding the first wafer by the grinding tool along the thickness direction of the first wafer at a first feeding speed to obtain a first intermediate wafer, wherein the first feeding speed is 0.5-1 μm / s, and the grinding tool grinds the first wafer by a depth of 8-15 μm; S220, keeping the carrier table rotating in a direction opposite to that of the grinding tool, and grinding the first intermediate wafer by the grinding tool along the thickness direction of the first intermediate wafer at a second feeding speed, wherein the second feeding speed is 0.3-0.8 μm / s, the second feeding speed is smaller than the first feeding speed, the grinding tool grinds the first intermediate wafer by a depth of 4-8 μm to obtain a second intermediate wafer; S230, keeping the carrier table rotating in a direction opposite to that of the grinding tool, and grinding the second intermediate wafer by the grinding tool along the thickness direction of the second intermediate wafer at a third feeding speed, wherein the third feeding speed is 0.1-0.5 μm / s, the third feeding speed is smaller than the second feeding speed, and the grinding tool grinds the second intermediate wafer by a depth of 1-4 μm.
4. The production method according to any one of claims 1 to 3, characterized by, In the step S200, the grinding aid is sprayed to the first wafer during the grinding process, wherein the dispersed substance of the grinding aid is one or more of metal oxide, metal sulfide or metal chloride, and the dispersion medium is water.
5. The production method according to claim 4, characterized by, The dispersed substance of the grinding aid is one or more of nano-zinc oxide and nano-zinc sulfide, and the volume fraction of the dispersed substance in the grinding aid is 1-4%.
6. The preparation method according to claim 4, characterized in that, The ground surface of the first wafer is a grinding surface, and an included angle α is formed between the grinding surface and the spraying direction of the grinding aid, wherein the included angle α is 45-90°.
7. The preparation method according to claim 4, characterized in that, The temperature of the grinding aid is 15-40℃, so that the temperature of the first wafer is kept not more than 100℃ during the grinding process in the step S200.
8. The method of any one of claims 1-3, wherein, The step S100 further comprises the following steps: S110, providing a carrier table carrying a wafer to be processed and a grinding tool for grinding the surface of the wafer to be processed, rotating the grinding tool and the wafer to be processed, and allowing the grinding tool to grind the wafer to be processed, wherein the rotating speed of the grinding tool is 2000 rpm-4000 rpm, and the rotating speed of the carrier table is 200 rpm-500 rpm; S120, single grinding the wafer to be processed along the thickness direction of the wafer to be processed at a feeding speed of 0.4 μm / s-1 μm / s, wherein the grinding depth of the wafer to be processed by the grinding tool is 3 μm-12 μm in the single grinding process, and the single grinding process is repeated for multiple times until the grinding depth of the wafer to be processed by the grinding tool is 20 μm-50 μm.
9. The method of any one of claims 1-3, wherein, After the step S200, the method further comprises a step S300 of cleaning and drying the carrier table and the silicon carbide wafer by using water-air two-fluid.
10. The method of any one of claims 1-3, wherein, The wafer to be processed is a 4H-SiC substrate material.